Without limiting the scope of the present invention, its background will be described with reference to producing fluid from a subterranean formation, as an example.
After drilling each of the sections of a subterranean wellbore, individual lengths of relatively large diameter metal tubulars are typically secured together to form a casing string that is positioned within each section of the wellbore. This casing string is used to increase the integrity of the wellbore by preventing the wall of the hole from caving in. In addition, the casing string prevents movement of fluids from one formation to another formation. Conventionally, each section of the casing string is cemented within the wellbore before the next section of the wellbore is drilled.
Once this well construction process is finished, the completion process may begin. The completion process comprises numerous steps including creating hydraulic openings or perforations through the production casing string, the cement and a short distance into the desired formation or formations so that production fluids may enter the interior of the wellbore. The completion process may also include installing a production tubing string within the well casing which is used to produce the well by providing the conduit for formation fluids to travel from the formation depth to the surface.
To selectively permit and prevent fluid flow into the production tubing string, it is common practice to install one or more sliding sleeve type flow control devices within the tubing string. Typical sliding sleeve type flow control devices comprise a generally tubular body portion having side wall inlet openings formed therein and a tubular flow control sleeve coaxially and slidably disposed within the body portion. The sleeve is operable for axial movement relative to the body portion between a closed position, in which the sleeve blocks the body inlet ports, and an open position, in which the sleeve uncovers the ports to permit fluid to flow inwardly therethrough into the interior of the body and thus into the interior of the production tubing string. The sliding sleeves thus function as movable valve elements operable to selectively permit and prevent fluid inflow. Generally, cylindrical shifter tools, coaxially lowered into the interior of the tubing string on a conveyance such as a wireline, slickline or coiled tubing, are utilized to shift selected ones of the sliding sleeves from their closed positions to their open positions, or vice versa, to provide subsurface flow control in the well.
It has been found, however, the once a sliding sleeve flow control device has been positioned within the wellbore for an extended period of time, the slidable sleeve may become stuck in a particular operational state and therefore difficult to actuate. In addition, even normal actuation operations may place significant demands on the integrity and strength of the shifting tool and the conveyance in wells that are deep, deviated, inclined or horizontal due to elongation of the conveyance and added frictional effects.
Accordingly, prior art shifting tools and conveyances can apply only a limited amount of shifting force to actuate a sliding sleeve flow control device previously placed into the wellbore. Therefore, a need has arisen for a shifting tool that will provide for the exertion of a greater shifting force such that well tools that are stuck in a particular operational state can be actuated. A need has also arisen for such a shifting tool that will produce the necessary force to actuate well tools positioned in deep, deviated, inclined or horizontal wellbores.